It is unlikely that the BooterCE patch will work without patching the Bootloader first. I expect that the Bootloader should be very similar to that of the x300t so it will check the signature of the NK.BIN.
So without JTAG I don't see a way of doing that.
But there should be another way in your case

The debug build of the BT-Vision Client has a content.sig file that doesnt have any effect since it has "BOOTABLE" flags for all files and those files are skipped during file validation phase.
That means you can modify any file without problems.
The only question is: does the debug build work on your client or does it need special developer boxes.
By the way... I checked out the media sharing. It is working on my box, but since you cannot share video files, it is not that useful

the client needs to be modified to also accept video files.... that should be doable.